No, you won't have to break out a Torx screwdriver to remove any internal components. But you probably will have to spend time uninstalling software that a theoretically helpful manufacturer loaded on the machine.

Start where your new computer will: with a round of system-software updates. Once Win 7 or OS X detects a network connection, each should automatically fetch updates for you; if not, click the Windows Control Panel's "Check for updates" link or select OS X's Software Update program from the Apple-icon menu.

(Even before you first log in, OS X will prompt you to transfer files, settings and applications from another Mac using its fantastically helpful Migration Assistant. Microsoft's Windows Easy Transfer program won't move over programs but is still an immense time saver; you, however, might as well save that until you're done with more basic chores.)

In Windows, the first thing you're likely to see after a Windows Update prompt is a nag from an Internet-security program bundled by the PC's vendor. This software is usually a bad deal: Microsoft's free, nag-free Microsoft Security Essentials (microsoft.com/securityessentials) won't ask you to pay for a subscription after the first 30 or 90 days.

So I'd dump the included anti-virus program by clicking the Control Panel's "Uninstall a program" link-after downloading MSE's installer and disconnecting the computer from the Internet. (Keeping two anti-virus programs active at once won't keep you safer but will make computing much more of a nuisance.)

On a Mac, you only have to turn on the system firewall that Apple inexplicably left off. Open System Preferences, click its Security icon, click the Firewall tab and click its Start button.